The present invention relates to a rotation angle sensor that includes a brushless resolver having a transformer and a magnetic rotor and to a method for winding a rotation angle sensor, and in particular, to a rotation angle sensor in which a rotor transformer winding and a magnetic rotor winding are wound with a single wire.
A brushless resolver has a transformer winding such that, in addition to the rotor and stator for excitation and detection, the resolver includes a transformer for a power supply. FIG. 5 shows an example.
FIG. 5 is a cross-sectional view of the structure on the rotor of a conventional resolver. The structure of the stator is omitted. FIG. 5 shows the rotor structure including a rotor 102 having bobbin 103 integrally formed with the rotation shaft 101 (the rotor winding is not shown in the drawing). FIG. 5 represents an improvement over a conventional rotor transformer structure in which the bobbin 103 from is formed separately from the rotation shaft 101 and combined later. The rotor winding and rotor transformer winding are individually formed, and then combined. (e.g., see Japanese patent publication JP H10-170306). Then, the rotor winding and rotor transformer winding are connected, and the connection is performed as described below.
FIGS. 6A and 6B show a conventional connection of the rotor winding and rotor transformer winding. FIG. 6A shows that a rotor having a magnetic rotor winding and a rotor transformer having a rotor transformer winding are mounted on a rotation shaft. FIG. 6B shows a state in which the lead wires of each winding shown in FIG. 6A are connected.
The coil bobbin 113 of the rotor transformer 112 is mounted on a winding machine (not shown in the drawing), and an electrical wire is coiled around the groove of the coil bobbin 113 for a predetermined number of times. Then the lead wire 122a at the starting side of the winding and the lead wire 122b at the ending side of the winding are temporarily fixed with an insulation tape (not shown in the drawing). Then, the lead wires 122a, 122b are led out from the winding machine.
Regarding the magnetic rotor 114, a laminated rotor core 123 is mounted on the winding machine and the electric wire is coiled for a predetermined number of times on each of many magnetic poles of the rotor core 123. The wire may be coiled directly on each magnetic pole or indirectly via a coil bobbin. Then, the lead wire 124a at the start of the winding and the lead wire 124b at the end of the winding are temporarily fixed with insulation tape, and then led out from the winding machine.
Next, a hollow rotation shaft 111 is inserted and fitted in the magnetic rotor 114 and the rotor transformer 112. Then, as shown in FIG. 6A, the magnetic rotor 114 and the rotor transformer 112 are positioned at predetermined locations on the rotation shaft 111. At that time, the magnetic rotor 114 and the rotor transformer 112 are arranged so that an opening 119 of the coil bobbin 113 of the rotor transformer 112 is located on the side of the coil bobbin 113 that faces the magnetic rotor 114.
When the magnetic rotor 114 and the rotor transformer 112 are positioned properly, insulation tubes 128 are mounted on the lead wires 124a and 124b. Then, the starting lead wire 124a and the ending lead wire 124b of the magnetic rotor winding 121 are led into the groove of the coil bobbin 113 via the opening 119. Then, while taking the polarity of the magnetic rotor winding 121 and rotor transformer winding 120 into account, the lead wires 124a and 124b of the magnetic rotor winding 121 are connected to the starting lead wire 122a and ending lead wire 122b of the rotor transformer winding 120, so that a series circuit is formed. The insulation coating of the electric wire will not be damaged by the edge of the opening 119 due to the insulation tubes 128.
In the case of FIG. 6B, the ending lead wire 124b and the starting lead wire 122a are connected with solder 126. Similarly, the starting lead wire 124a and the ending lead wire 122b are connected with solder 127. The soldered connections are made along insulation tape 125, which is attached to the surface of the rotor transformer winding 120, and fixed with resin. This method has the following problems.
Conventionally, a semi-finished product has been manufactured for each unit. That is, a semi-finished rotor component, in which the magnetic rotor winding is coiled and its lead wire is temporary fixed with tape, and a semi-finished rotor transformer component, in which the rotor transformer winding is coiled and its lead wire is temporarily fixed with tape, are individually formed. Then, an alignment process in which the rotation shaft is inserted in the components is carried out. The alignment is difficult because the finished winding may be mistakenly deformed by being pressed manually or the temporary insulation tape may detach, and the predetermined shape of the coiled winding may be destroyed.
In addition, when the lead wires of the magnetic rotor winding and the lead wires of the rotor transformer are connected, the lead wires of the magnetic rotor winding are covered with insulation tubes 128 and then fed through the opening 119. Then, the lead wires 124a, 124b, 122a, 122b are connected at two junctions, and the two junctions are placed along the rotor transformer winding via insulation tape and fixed with resin. The process is difficult to carry out in a small space, and thus, long lead wires must be employed. Unlike the winding portion, the long lead wires may generate an irregular magnetic field that has an effect on the basic magnetic field, which is based on the designated number of windings, and may create an uneven weight distribution, which may cause oscillations during the rotation. Further, the long lead wires may cause a restriction such that the interval between the rotor transformer and magnetic rotor cannot be narrowed.